This invention relates to fluid filters and, more particularly, to a plastic fuel filter that can separate contaminating water from the fuel, and a method for manufacturing such a filter.
The filter art includes various filters that can separate water from fuel, known as fuel water separators. See, e.g. U.S. Pat. Nos. 3,297,160; 3,502,218; 4,253,954; 4,676,895; and 4,740,299. These filters are often used in diesel fuel systems for trucks.
U.S. Pat. No. 4,740,299, in particular, relates to a metal housing for a paper filter media that is directed to separating water from fuel. More specifically, this filter includes the following components: a drawn cylindrical metal housing having two open ends; a plastic, threaded adaptor ring fixedly and sealingly received at one open end via a structural adhesive; a cylindrical filter element placed within the housing, made of pleated filter media paper surrounding a metal center tube, and terminated by metal circular end caps; a thick metal end plate including a threaded central outlet aperture and radial inlets; one of several gasket retainers is attached exteriorly to the end plate depending upon which gasket diameter is required, the end plate/retainer combination being attached to the other open end of the filter housing by seaming the interface thereof; a rubber grommet between one of the end caps and the end plate; a gasket received in the gasket retainer; and a separate plastic collection bowl screwed onto the threaded adaptor. The complete filter is screwed onto a threaded post formed on a mount in a fuel line via the threaded central aperture of the end plate.
During use, which occurs at about up to 40 p.s.i., diesel fuel is introduced through the mount and circulated inside out relative to the media. The conventional water-stripping media causes water present in the diesel fuel to coalesce on the outside of the media. The bowl collects the separated water after it runs down along the outside of the media and across the adaptor. When the filter has reached its capacity, the old filter is removed from the mount, the bowl is removed from the filter housing and emptied, a new filter housing is screwed onto the mount, and the same bowl is screwed on the new filter housing.
The manufacturing steps for producing such a filter include basically the following: the housing is drawn; media paper is pleated, cured, cut and clipped to form a cylinder; the center tube is inserted in the media cylinder and the end caps are attached to the media via Plastisol and cured to form a media element; the adaptor receives the adhesive, which is very expensive, and the adaptor is positioned in the housing; the rubber grommet is added to the element and the element is placed in the housing; and the end plate/gasket retainer combination is formed and sealed to the other end of the housing.
This filter, since it includes numerous parts that must be stamped, molded and/or seamed, and since it depends upon a multi-step manufacturing process, is relatively expensive to produce.
Further, this type of filter is relatively environmentally unfriendly. That is, the filter includes metal, paper, rubber and plastic components. It is very costly, time-consuming and labor intensive to recycle such a multi-component product after use. Many states are currently considering steps to tax the disposal of used metal oil filters or simply refuse to dispose of same in landfills.
Separately, the filter art has made attempts to provide filters that rely more on plastics in an effort to minimize the material costs, parts and assembly steps. These plastic filters, however, do not appear to have proved commercially successful. For example, some attempts related to plastic automotive oil filters have suffered because the plastics chosen have not been able to withstand the significant temperature and pressure associated with oil filters. These filters also may not decrease the manufacturing steps or raw material costs, and they may not be particularly well-suited for recycling.
U.S. Pat. No. 5,171,430, relates to a filter assembly for fluids in which the filter has a unitary shell including an injection molded threaded end and an integral blow molded closed end, a replaceable filter element and a threaded end plate. While this patent indicates a goal of cost effectiveness, the fact that separate injection molding and blow molding steps must be performed thwarts this goal, because such multiple molding steps would be relatively expensive.
Although the prior art described above eliminates some of the problems inherent in the filter art, the prior art above still does not teach a plastic fluid filter and related method of assembly capable of the most cost-efficient production, the most reliable operation, the most environmentally friendly filter, or the most time-efficient automated assembly.